As the hydrated soft contact lens, there are hydrated polymers containing a hydrophilic monomer such as 2-hydroxyethylmethacrylate and vinyl pyrrolidone as their major components. The hydrated soft contact lens is known to have a good wearing feel due to the flexibility of the material thereof. Also, it is known that the oxygen permeability of the hydrated soft contact lens is generally dependent on the moisture content of the lens. However, in the case of a polymer primarily using vinyl pyrrolidone which is a highly hydrated soft contact lens material as its major component, its oxygen transmission coefficient is about 50×10−11 (cm2/sec)·(mLO2/mL×mmHg) even if the moisture content is 80% and it is not therefore said that oxygen is supplied in a sufficient amount to the cornea. Also, since the lens is highly hydrated, it is easily contaminated, causing a deterioration in wearing feel and the angle of vision when it is used for a long period of time. Specifically, the conventional hydrated soft contact lens has insufficient oxygen permeability though it has a good wearing feel, giving rise to, for example, the problem that the cornea is put into an oxygen deficient state, causing the onset of grave symptoms.
Because the continuous wearing of a contact lens is the main current in recent years, high oxygen permeability is a necessary and essential element and further, higher wettability of the surface of the lens is desired to exhibit soil resistance which can stand against continuous wearing. If a silicone type monomer is used as a lens raw material, it causes the lens to be highly hydrophilic, though high oxygen permeability is obtained. Therefore, because the lens is caused to be highly hydrophobic, it becomes cloudy when it is utilized for a hydrated soft contact lens and it is hardly avoidable to drop the moisture content of the lens. As a result, the raw material itself is hardened, causing a deteriorated wearing feel and also, the surface of the lens to exhibit deteriorated wettability, which is eventually a cause of a dry feel and the deposition of soils contained in lachrymal components.
In the case of a hydrated contact lens using a silicone type monomer, under this situation, there are large problems as to a proper moisture content and an improvement in the wettability of the surface of the lens. Therefore, there are various proposals concerning materials used for silicone-containing hydrated contact lenses having high oxygen permeability and wettability.
There is a disclosure of, for example, technologies in which a silicone hydrogel contact lens comprising a silicone macromonomer, a bulk polysiloxanyl(meth)acrylate monomer and a lactam-containing monomer is subjected to plasma surface treatment and then, hydrated (see, Patent Reference 1). However, this method has, for example, the problems that it needs very large-scaled equipment such as a plasma treating apparatus and that it is complicated in the design of conditions for forming a film.
There is also a disclosure concerning an ocular lens material obtained by copolymerizing a polysiloxane prepolymer capped with an acryl group, a bulk polysiloxanyl(meth)acrylate monomer and a hydrophilic monomer (see Patent Reference 2). This material is obtained in the form of a low modulus hydrophilic gel by combining two different silicone components, that is, a polysiloxane prepolymer and a bulk polysiloxane type monomer. This material has a moisture content of about 17 to 43% and an oxygen transmission coefficient of about 60 to 150×10−11 (cm2/sec)·(mLO2/mL×mmHg). Since this material has a low modulus, posing the problem of the stability of the shape of a lens and also, it is not said that sufficient consideration is given to the wettability of the surface of the lens.
In the meantime, an ocular lens material comprising a siloxane-containing polymer obtained by polymerizing a siloxane macromonomer with a lower fatty acid vinyl ester (see Patent Reference 3) and an ocular lens material comprising a macromer having a polysiloxane at its side chain (see Patent Reference 4) are disclosed as non-hydrated ocular lenses having flexibility and shape recoverability. The siloxane macromonomer which is a major component in these ocular lenses has a urethane group in each structure and imparts mechanical strength, flexibility and wettability. However, a urethane bond is hydrolyzed relatively easily and it is therefore estimated that when this siloxane macromonomer is used in a large amount for use as a hydrated ocular lens, the polymer becomes cloudy and is deteriorated in the function as an ocular lens. Also, when the amount of the siloxane macromonomer to be used is reduced, a polymer having entirely satisfactory oxygen permeability is not obtained. Also, if the siloxane bond part in a molecule is increased to improve oxygen permeability, the compatibility with other copolymer components is deteriorated, so that a polymer which is transparent and has good mechanical strength is not obtained and it is therefore difficult to use as an ocular lens.    Patent Reference 1: Japanese Patent Application National Publication (Laid-Open) No. 2002-513948    Patent Reference 2: Japanese Patent Application Laid-Open (JP-A) No. 2003-268055    Patent Reference 3: W/O 00/70388    Patent Reference 4: JP-A No. 13-311917